Breeding alters cuticular hydrocarbons and mediates partner recognition by burying beetles

In many insects, recognition cues for social status or family membership are based on differences in cuticular hydrocarbons. In some cases these cues reflect reproductive status. Burying beetles, Nicrophorus orbicollis, form temporary pairs to rear a brood and, as a pair, they must defend their young and the breeding resource (a small vertebrate carcass) from conspecific intruders. Thus, a mechanism for the identification of a nonpartner is necessary for the appropriate aggressive response. Burying beetles appear to use reproductive status to identify partners. In behavioural tests of recognition, unknown individuals at the same reproductive stage were accepted as mates. In addition, males showed significantly less aggression towards unknown nonbreeding females treated with an extract of their mates' cuticular hydrocarbons. Cuticular hydrocarbon profiles of males and females on the sixth day of breeding, the most intense phase of parental care, were significantly different from those of their nonbreeding counterparts, but quite similar to each other. We conclude that these hydrocarbon profiles change during a breeding bout and mediate recognition of breeding partners. Furthermore, although juvenile hormone haemolymph titres changed dramatically during breeding, they did not directly affect hydrocarbon profiles.